Diel Vertical Migration of zooplankton in a eutrophic bay of Lake Victoria
Loading...
Date
2009
Journal Title
Journal ISSN
Volume Title
Publisher
Hydrobiologia
Abstract
We studied the Diel Vertical Migration
(DVM) of several zooplankton taxa and an important
zooplanktivore Rastrineobola argentea in a eutrophic
bay of Lake Victoria for a total of 3 months during
wet and dry seasons. Zooplankton were sampled
twice a month at full moon and new moon. The
zooplankton community of this lake was numerically
dominated by cyclopoid copepods ([80%) of which
80% were juveniles. The composition of zooplankton
was not significantly different (P[0.05) for the
different sampling months (November 2000, March
2001 and July 2001), but total zooplankton abundance
was significantly lower (P\0.05) in July (dry
season) than during March or November (wet
seasons). DVM behaviour was observed in some of
the zooplankton groups including Tropocyclops spp.,
Thermocyclops spp., Thermodiaptomus galeboides
and Diaphanosoma excisum. In these groups, we also
observed that they were significantly (P\0.05) more
abundant at full moon than at new moon in some
months, a pattern not seen in non-DVM groups. The
amplitude of migration tended to be higher at new
moon than full moon for all DVM zooplankton but
not significantly so (P[0.05). The zooplanktivore
R. argentea exhibits typical DVM behaviour, perhaps
to avoid visual predation itself, but it also increases the
predation pressure on zooplankton in deeper waters.
Feeding times for R. argentea peak just after dusk
and dawn. For the copepod calanoid T. galeboides,
there was a strong relationship (P\0.05) between
the amplitude of migration and midday (12:00) water
transparency, suggesting that these zooplankton may
have descended deeper on days with higher water
transparency. In the absence of temperature and food
gradients but with predation pressure from a migrating
zooplanktivore, the depth of descent of zooplankton
may be well associated with water transparency.
Description
Keywords
Lake Victoria, Zooplankton, Diel Vertical Migration, Murchison Bay
Citation
Semyalo, R., Nattabi, J. K., & Larsson, P. (2009). Diel vertical migration of zooplankton in a eutrophic bay of Lake Victoria. Hydrobiologia, 635(1), 383-394. DOI 10.1007/s10750-009-9931-5